This master thesis is a part of the project TAČR TREND, which aim is the development of new ingredient for treatment of dry eye syndrome. Developed ingredient is derivative of hyaluronic acid, which is in this thesis compared with native hyaluronic acids and commercial eye drops. Aim of this thesis is to describe rheological and tribological properties of measured samples in terms of viscosity, mucoadhesivity and coefficient of friction. Coefficient of friction was measured on created tribological model of the eye in pin-on-plate configuration which represents physiologically relevant sliding speeds of blinking. Comparison with native hyaluronic acids and commercial products of eye drops showed, that derivative reaches higher values of viscosity, has mucoahesive properties and has low values of coefficient of friction. Those key parameters show that modification of hyaluronic acid is promising way for drug development for dry eye disease.

Available instruments for viscosity and rheologic measurements necessitate disruption of the system under test prior to observations. Generally, the gel structure of a thixotropic clay must be disturbed by shaking, pouring into a container for testing, and again upon insertion into the sample of the bob, spindle or paddle of the instrument. Also, these instruments yield a single point reading which is only a final or average value, depending upon the instrument. The occurrences during the test itself cannot be observed. Accordingly? it seemed feasible to determine, if possible, what other rheologic factors are involved in the breakdown of ·the gel structure of a thixotropic clay dispersion. The objective of the study was to design and test an instrument which would not require disturbing the sample before testing, which would give minimal destruction of the sample upon entry of the test probe into the sample, and which would give complete permanent recordings throughout the time of testing.

This work deals with preparation of layers of ceramic materials – perovskites. The introductory part includes general characteristics concerning structure, properties and use of this materials. In details then there is described method of their preparation, namely Pechini´s syntheses, which are most widely used. Optimum molar ratio of components is discussed, in the sense of what compositions lead to creation of perovskite structures. Influence of this parameter on rheological properties of precursory gels is described in the end of the first part of work. In experimental section there are described preparations of gels, which are prepared via reaction between citric acid and ethylene glycol and gels, which are prepared by Pechini´s synthesis. Rheological properties of prepared gels (density, viscosity and surface tension) and besides determination of amount of nitrates in gels are characterized. Temperature dependence of viscosity of gels, that are prepared by reaction of citric acid and ethylene glycol are determined. In final part successful preparations of perovskite layers is shown on ceramic substrate. This layers are observed by means of light optical microscope and scanning electron microscope.

The thesis is focused on physical hyaluronan gels. The object of study is the interaction of hyaluronan (HyA) with oppositely charged surfactants in physiologic solution (0.15 M NaCl), leading to the formation of gel. In the first part of work have been determined the solids´ contents (X) in gels and their supernatants in percentage and their correlation with molecular weight concentration of original HyA solution and the ratio of binding sites on hyaluronan chain and surfactant CTAB. To conclude, decrease in HyA concentration results in higher values of X and vice versa. On the other hand, increase in the value of X with increasing molecular weight of HyA is not so significant. Analogous conclusions have been made for supernatants and the amount of solids in gel. Drying process has been recorded by drying curves. Swelling process has been used for the characterization of gels. The percentage of water that can be absorbed by dried gel, was determined. The results are in agreement with the measurements of solids´ content in gels. In the next part, the correlation between rheological properties of gels and HyA concentration, HyA molecular weight and concentration of CTAB have been studied by the oscillation and flow tests. The samples with the highest molecular weight and concentration have the most viscoelastic character. The flow test confirmed the assumed pseudoplastic behavior of gels. A very interesting trend arose while comparing HyA concentrations and viscosity in stock solutions and gels. Whereas in stock solution viscosity (at low shear rate) is lower with increasing of HyA concentration, the situation was exactly the opposite in gels. The results are in agreement with frequency tests and observed character of gels.

Diplomová práce je zaměřena na přípravu koloidních suspenzí, vytvrditelných UV zářením, jenž jsou určeny k 3D tisku komplexních keramických vláknových struktur. Rovněž jsou v práci představeny techniky následného tvarování vytisknutých a vytvrzených struktur. Z hydroxyapatitu ve formě prášku a komponent, vytvrditelných UV zářením, byly vytvořeny pasty, určené k 3D tisku komplexních keramických vláknových struktur a multivrstev. U takto vytisknutých a vytvrzených struktur bylo navíc dosaženo zlepšení kvality povrchu a soudržnosti vláken. Pro výrobu past, určených k 3D tisku, s vhodnými reologickými vlastnostmi je nezbytné důkladné pochopení interakcí mezi částicemi, surfaktantem a monomerní/oligomerní směsí. Za použití lineárních a zesíťujících oligomerů jako disperzního média vznikají po tisku a UV vytvrzení velmi flexibilní vláknové mřížky, které lze dále tvarovat a takto vytvářet rozmanité struktury. Tyto struktury jsou následně slinuty, bez významných vad na povrchu či delaminace vrstev, za vzniku složitých keramických těles. Vysoké kvality povrchu je dosaženo UV vytvrzením vytisknutých struktur v argonové atmosféře, která brání kyslíkové inhibici radikálů v blízkosti povrchu vláken. Výhody kombinace 3D tisku s UV vytvrzováním jsou demonstrovány v této práci za užití dvouvrstvých flexibilních struktur, určených k následným metodám 3D tvarování. Takto vytvořených složitých 3D struktur je jen velmi obtížné, ne-li nemožné, dosáhnout pouze užitím přímého 3D tisku. Na základě této práce může být v budoucnu odvozena univerzální teorie k přípravě past, určených k 3D tisku komplexních keramických struktur pro různé aplikace.

Collagen, the most abundant protein of connective tissues, in various forms has a wide applications due to their diverse biological and chemical properties. One of the forms are collagen hydrogels, which are considered very suitable material for applications in tissue engineering, because they are able to provide biodegradable scaffolds that its properties correspond with living tissues. These systems are used for example as scaffold for targeted drug delivery with controlled release, in combination with cells can be used for the regeneration and reconstruction of tissues and organs. Heating the aqueous solution of collagen leads to spontaneous self-assembly process to variously distributed fibrillar structures, which are at a later stage of fibrillogenesis prerequisite for creating a three-dimensional supporting network, which is the basic building block of the gel. The resulting properties of the hydrogel depend not only on its structure, but also on the conditions which cause self-assembly process. Hydrogels were performed at 37 ° C and physiological pH. Studied structural variable was the concentration of collagen. So far, for the research of self-assembly were used spectrometric methods, which only provide information about kinetics of morphogenesis. In this work to study the kinetics of collagen I self-assembly were used rheological methods, which additionally give information about viscoelastic properties of the resulting material. The obtained experimental data confirmed two-step process of collagen I fibrillogenesis consisting of nucleation and growth process. Rheological hydrogels collagen behaved as a nonlinear yield-pseudoplastic. An attempt was made to molecular interpretation of the results. Using two-parametric Avrami equation was determined the rate of self-assembly for each concentration of collagen and the value of Avrami exponent determining the shape of produced units. The prepared hydrogels were subjected to increasing shear stresses (strain amplitude, shear rate). Larger amplitudes leads to collapse of the hydrogel structure, which is able to again partially regenerated.

The main aim of the doctoral thesis was study of passive microrheological techniques as advanced methods for characterisation of viscoelastic properties of soft material. These techniques are able to provide certain advantaged or additional information on classical rheology. Several techniques from the wide range of passive microrheological group such as one particle video – microrhelogy with IDL data procesing, microrheology based on light scattering – DLS or FCS microrheology have been applied in practice during my PhD studies. New Matlab script has been also invented to simply obtain information about viscosity of low volume samples. Aplicability of techniques were studied on several various bicolloids such as solutions or gels of hyaluronic acid, on study of properties at the interfaces or on gelation proces studies of agarose. Obtained data were compared classical rheology results. Suitability of each technique for investigated systems or appropriate reccomendations for further measurements were didcussed based on obtained data. Main advantages and limites of passive microrheology techniques were also described in comparison wih classical rheology method.

The presented thesis on thermosensitive polymer gel is focused especially on a thermosensitive triblock copolymer, which is composed of hydrophobic polylactide, polyglycolid and hydrophilic polyethylene glycol (PLGA-PEG-PLGA). Thermosensitive copolymers are very attractive for their phase sol-gel transitions and gel-suspension transitions. The aqueous solution of this copolymer behaves like a sol at laboratory temperature and like a gel at body temperature. These systems are used as injectable carriers for targeted drug delivery with controlled release. However, the influence of the resulting polymer concentration and temperature on the thermosensitive hydrogel nanostructure was not yet fully studied. In the experimental part, the viscoelastic behavior of hydrogels was observed by dynamic rheological analysis at different polymer concentrations and temperature conditions. The average size and distribution of micelles of triblock copolymer in aqueous solution were measured using dynamic light scattering technique. Characterization of fibrous micelles was complemented by imaging technique, cryogenic transmission electron microscopy.

This diploma thesis deals with preparation and subsequent characterization of albumin (BSA) and mixed hyaluronan-albumin (HA+BSA) hydrogels. The experimental characterization was based on the rheological measurements of the influence of ionic strength, pH and molar mass of HA on the gelation process and the properties of formed gels, as well as the time stability of these properties. Following object of the study was swelling of hydrogels in water and buffers with different pH value. Characterization was extended by thermal analysis, morphology description using scanning electron microscopy (SEM) and study of transport properties of hydrogels for selected model substance. Due to increasing ionic strength, the gel point was shifted towards higher temperature values and the resulting gels exhibited higher values of complex moduli. In case when pH was lower than isoelectric point of BSA, attractive electrostatic interactions between albumin and hyaluronan took place and the faster gelation occurred, compared to the case when pH was higher than isoelectric point of BSA. On the contrary, values of complex moduli increased with increasing pH. The gel samples prepared in the presence of low molecular weight HA reached higher values of complex moduli, compared to samples with the high molecular weight HA. Rheological properties of BSA gels were stable over time, whereas the mixed HA+BSA were characterized by significant decrease of complex moduli during the first three days of storage. Due to heating up to 100 °C, more than 80 % of the weight of studied samples was lost, as a result of water evaporation. Further heating of hydrogels, up to 250 °C, did not cause other changes associated with weight loss, in contrast with crystalline powder BSA, in which another weight loss at 220 °C was observed, as a result of the beginning degradation. Swelling studies, as well as SEM images, indicated higher crosslink density of BSA gels, compared to HA+BSA samples, which exhibited higher values of swelling ratio. The lowest values of equilibrium swelling ratio were observed at pH 4, which is close to the isoelectric point of albumin. Calculated diffusion coefficients relative to diffusivity of methylene blue in water ranged between the order of 10E-2 for diffusion into physiological solution and the order of 10E-3 for the diffusion into water. Ongoing transport of model dye from gel to solution was significantly slower, compared to its diffusion in water, as a result of gel porosity and electrostatic immobilization of positively charged molecules of methylene blue on the negatively charged BSA and HA chains.

This diploma thesis was focused on the system of agarose hydrogels with micellar domains. Polysaccharide agarose was used for the preparation of hydrogel matrices. Septonex was chosen as a surfactant. The release of solubilizate from the agarose hydrogel matrix was studied with a hydrophobic dye Sudan III in order to obtain a model system of hydrophobic solubilized drugs. Sudan III was solubilized via surfactant´s micels. Subsequently, this micellar aqueous solution with the dissolved dye was used to prepare the agarose hydrogel. The system was prepared in the environment of deionized water and physiologic solution. The gradual release of the dye into deionized water and physiologic solution was studied for 22 days using the UV-VIS spectrophotometry method. It was found that after 14 days the concentration of the releasing dyes into the deionized water was decreased. The cause is that after 14 and 22 days there was a slight degradation of gels, which was detected using the rheology method. Using the rheology method it was also found that Septonex does not affect the gel formation process.